Geology. 331 



and other facts of interest and importance. It would appear, at 

 first sight, that a large number of new genera are proposed, and 

 that most of the old familiar genera are present under unfamiliar 

 guises, but a closer inspection shows that the number of actual 

 new names is few. The others are rehabilitated terms, nearly 

 forgotten since their origin, and now re-defined and applied to 

 distinct groups of forms or types of structure. Thus the subject 

 has been simplified by breaking up many of the old heteroge- 

 neous groups, such as Discina and Orthis, into clear cut minor 

 genei'a or subgenera, which are now available for accurate sys- 

 tematic work. The authors have abstained from the exact use 

 of family or other taxonomic designations except the two great 

 divisions Inarticulata and Articulata. 



Lingula is the first genus discussed, but it is not necessarily 

 considered as the primitive type of inarticulate brachiopods. 

 This view is supported by the geological history, anatomy, and 

 development. Lingidella and Lingulepis are regarded as fore- 

 runners of Lingula, and connecting links to the Obolelloid type. 

 Modifications of the nature of septa produced by the deposition 

 of shell} 7 matter about the muscular and parietal bands produced 

 related genera, such as Dignomia and Glottidia. Special 

 features developed about the cardinal areas resulted in forms for 

 which the new generic terms Barroisella and Tomasina are pro- 

 posed. Other structures arising from mechanical necessity, as 

 the elevation of the anterior edges of the muscular attachments 

 to compensate for hepatic and ovarian pressure resulted in the 

 formation of the vaulted platform of Lingulasma. The authors 

 consider this feature of much importance. It first appears in 

 Lingulops, and reaches a higher development in Lingulasma. 

 Whether this character in these genera is in direct genetic line 

 to Trimerella, or whether it is a morphological equivalent, may 

 be questions for further discussion. 



Among Discinoid shells the new genus Discinopsis of Matthew 

 is first defined, and the subgeneric divisions of Orbiculoidea, 

 GEhlertella, Lindstrcemella, and Roemerella, are proposed, based 

 upon the features of the pedicle opening and form of the ventral 

 valve. Of especial interest and importance are the observations 

 on the development of the pedicle opening in Orbiculoidea, 

 iSchizocrania, Trematis, and Discinisca, showing their genetic 

 relations in that Discinisca and Orbiculoidea pass through 

 young stages comparable with adult conditions of Schizomania. 



Besides the current terms Platystrophia, Bilobites, Schizo- 

 phoria. etc., founded upon groups which have been separated 

 from Orthis, the authors have introduced seven new divisions 

 making altogether fourteen including Orthis as restricted. The 

 new names proposed are : Plectorthis, Dinorthis, Plaisiomys, 

 Hebertella, Iieterorthis, Dalmanella, and Orthotichia. Three 

 new names are also applied to forms related to Glitambonites 

 (= Orthisina d'Orb.) ; viz. Billingsella, Protorthis, and Poly- 

 tcechia. 



